Common IssuesSFS provides solutions for design and final product verification, puddling and more. Standard impedance tolerances are within 10%. However, our engineering team routinely produces Controlled Impedance PCBs to hold 5% impedance tolerance. SFS achieves this by maintaining a database of past stackups and resulting thicknesses allowing our front end engineers to run tight impedance calculations. Further, numerous in-process checks are made to insure that fabrication results are as close to the designed values as possible.